1. Field of the Invention
The invention concerns an arrangement of cross-flow heat exchanger units, so-called modules, having ribbed surfaces, in a housing equipped with inlet and outlet openings for a primary stream and a secondary stream.
2. The Prior Art
Heat exchangers of the cross-flow type find applications, for example, in the process technology of the recovery of heat from exhaust gases. When it is desired to increase the capacity of such heat exchangers, it is possible, for example, to increase the heat exchange surface between the heat releasing and the heat absorbing media. However, this usually leads to an increase in the volume of the heat exchanger structure. In order to eliminate this disadvantage, the heat exchanger surfaces are provided with ribbing, which enhances the exchange of heat but also leads to an increase in the loss of pressure. DE-OS No. 26 15 579 disclosed an arrangement of heat exchanger units with corrugated ribs, wherein so-called core units are arranged spaced-apart at intervals. Flow through the units results in a series or in a partially-parallel manner.
This arrangement was chosen so that the individual heat exchanger units would be more accessible and thus easier to clean. The arrangement is not intended to improve performance; on the contrary, the connection in series of the individual heat exchanger units is detrimental to the thermal capacity of the entire installation. Thus, because of the intermixed arrangement of units with series and parallel flows, differing pressure losses and strongly-differing temperatures are obtained between the primary and the secondary flow. This constitutes one of the reasons why this known system cannot be arbitrarily enlarged to accommodate a higher level of heat exchange.
Swiss Patent CH-PS No. 588,672 also proposes an arrangement of cross-flow heat exchanger units, in which the units are arranged singly or in series-connected multiples in a housing, with bilateral flow through them. This arrangement has the aforedescribed disadvantage of poor thermal efficiency as the result of the diminishing mean temperature difference. Further, the system cannot be combined into large structural units, because an increase in losses of pressure would result.